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Animal breeding and selection

This document discusses animal breeding and selection. It covers several key points: 1) Genetic improvement is the goal of any breeding program and is influenced by both genetics (G) and environment (E). 2) Selection considers the whole population, not just individuals. Tools like EPDs and performance records are used. 3) Traits like growth, reproduction, and longevity should be breeding goals. Methods like individual, family, and progeny testing are used for single or multiple trait selection. 4) Crossbreeding can increase performance through hybrid vigor/heterosis and breed complementarity compared to purebreeding. Organized crossbreeding systems maximize these benefits.

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Animal Breeding andAnimal Breeding and SelectionSelection
Critical Questions to Ask • Genetic improvement, it is all about the male or the female? – The buck/ram contributes 50% of the genetic material in a flock and if his daughters are kept that number increases to 87.5% • But is that enough? • Pure or Cross Breeding system, which is better?
The Whole Picture • P = G + E • Where P is Phenotype can also mean production • G is Genotype • E is Environment in which the animal is raised, i.e. nutrition, health program, housing, temperature, humidity, parasite challenge, etc. • Changing G is the overarching goal of any breeding programme
Impact of Nutrition on Herd Productivity (an example of Environmental effects on production)
The Whole Picture • The individual animal is not the main objective in genetic selection but the population as a whole • The success of the programme depends on the breeding goals, record keeping and management
Selection tools 1) General visual appraisal-most common 2) Breeder records 3) Performance data for sires 4) Expected Progeny Differences (EPDs) 5) Show records 6) Pedigree data 7) Industry standards 8) Breed standards
Animal Selection • Takes daily attention – Collection of data – Observing the herd for conformation, disposition, behaviour – Mating selection – Selection of females
Breeding Goals • Lifetime Productivity – focuses on survival, fertility and prolificacy, udder characteristics and milk production, growth rate and ability to maintain body condition
Lifetime productivity for the doe/ewe • Selections are made based on: Fertility level, Prolificacy, Milk production, Genetic merit in growth, Seasonality in fertility and Health – Example: Selecting a doe with 3 kid crop in 2 years • Doe’s useful productive life is 5.33 years: • 14 kids produced • 13 kids raised • Kids weaned at 100 days weighing 22-25kg each
Reproduction and Culling • Culling is one of the best management tools that can be used – 10-20% culling rate is often employed • Keeping does/ewes with higher reproductive performance – Reproductive efficiency of the herd is determined by the kidding and weaning rates • Prolificacy is also important – 1 kid per year minimum, 1.5 ideal
Prolificacy of the Herd • Calculated by the total number of kids born over the total number of does kidded in a season x 100: • Percent herd prolificacy = # of kids born/# of does kidded x 100 • Percent herd weaning rate = # of kids weaned/ # does mated x 100
Generation Interval • The time lapse between birth of an animal and the birth of its replacement – usually 3-4 years for sheep • A measurement of progress or rate of improvement • Genetic Improvement per year = heritability x selection differential divided by the generation interval
Methods of Selection for Single Traits • Individual selection-selection on their own performance • Family selection-selection based on bloodlines • Pedigree selection-similar to family and is dependent upon how closely related the ancestors. Useful when considering same sex
Methods of Selection for Single Traits • Progeny Test- observing the performance of the offspring. – Must be mated to several ewes/does and then look at the offspring. – Best when looking at carcass traits • Combined Selection- uses more than one of the above mentioned methods
Methods of Selection for Multiple Traits • Tandem Selection- focuses on multiple traits, yet one at a time. After the performance of one is achieved, then move to the next trait • Independent Culling- Set minimum standards for more than one trait at a time for the indiv. Cull any that does not meet the min. stds for any trait
Boer Goats • Dark red head • Lop ears • Horns that curve backwards • Strong • Vigorous • Well-balanced
Boer Goats • Bucks mature to 300lbs. • Does should be feminine yet strong. • Does breed easily and have fast growing kids. • Does have high productive kidding rate of about 200%. (twins most of the time) • Extended breeding season, which allows her to produce three sets of offspring every 2 years.
Conformation • Subdivided into head, neck, forequarters, body, hindquarters. • Heads of the goats are very standard. • Determine age by toothing! • Two-teeth (1-1.5 years) with no over or under bite. • Four-teeth (1.5-2 years) can have an overbite.
Conformation • Strong horns • Broad ears, smooth, medium in length. • Short ears, concave foreheads, straight horns, overshot jaws, and blue eyes are not acceptable.
Skin & Covering • Loose supple skin • Folds in neck and chest region especially in bucks. • This type of skin helps to adapt in hot climates. • Eyelids and other hairless areas are pigmented to prevent sunburn. • Short glossy hair and limited amount of winter growth.
Ideal Boer Goat • Red hair on head and ears and white on the remainder of the body. • Face hair may vary from dark to light red and even brown. • The face has a white blaze. • Ears should be 80% color pigmented. • Head should be 50% colored.
Selection of Meat Goats • Conformation – (structural correctness) • General Appearance – (size, scale, capacity, depth and width of body) • Muscling – (growth and weight per day of age) • Condition – (amount of finish or fat the animal is carrying)
Selection and Evaluation • Goats deposit fat internally before they do externally. • Ideal condition is a thin, but uniform covering over the loin, rib and shoulder. • The external fat thickness over the loin at the 13th rib should be .08 in. to .12 in or an average of .10 in.
A Good Meat Goat has: • Fairly level rump • Level overall body shape • Straight level top • Length of rump • Length of body • Length of leg for market desirability • Straight legs placed square under body • Muscle in leg • Muscle in hindquarters, loin, shoulders, and neck.
Animal Selection
Animal Selection
Animal Selection
Selection for Growth • Growth is a very important trait, esp. for meat breeds • Adjusted 90 day weaning weight • If birth weight is known: • [Actual wt. - birth wt. x adj. Days (90)/ actual age ]+ birth wt. • If birth wt. is not known: • Actual wt. X adj. Age in days/age
Importance of Genetic Improvement in Seedstock Flocks • Most produce their own replacements • Therefore, genetic improvement from outside is by the Buck/Ram purchased • Theoretically, Genetic merit increases at the same rate as the genetic merit of the bucks/rams, yet because of generation intervals and replacement production usually improvement lags two generations behind
Mating Systems • Purebreeding- common genetic group • Outbreeding- unrelated within a breed • Inbreeding-closely related with one or more common ancestors (more than 50% related) • Linebreeding-common ancesters, but not 50% related • Crossbreeding- mating of different breeds • Grading Up-enhanced concentration of crossbreeding to bucks/rams of a single breed
Crossbreeding • Heterosis or Hybrid Vigor • Superiority of the crossbred indiv. Relative to the average performance of the parents • Maximized when parents have no breed ancestry in common (3 breed terminal X)
Crossbreeding Systems • 100 ewe flock • All ewe replacements are produced within the flock • All rams are purebred and purchased. • No pure Dorper ewes are used.
Crossbreeding Systems • Two Breed Terminal(50% Heterosis) • Three Breed Terminal (100%) • Three Breed Rotational (86 %) • Four Breed Rotational (93 %) • Two Breed Rotational
3-Breed Terminal Crossbreeding System Rambouillet rams x 55 SuffxDorper ewes Suffolk rams x 25 Dorper ewes Dorper rams x 20 Dorper ewes Market Lambs Male lambs and a few cull ewe lambs All Rambouillet-sired lambs Advantages: Good breed complementarity Disadvantage: Too many purebred ewes – reduced maternal hybrid vigor 40 kg lamb weaned per ewe exposed
3-Breed Rotational Crossbreeding System Dorper rams x H(SD) ewes Hampshire rams x SxD ewes Suffolk rams x Dorper ewes Market Lambs Advantages: All ewes (after start) and all lambs are crossbred – good use of individual and maternal hybrid vigor (86% of maximum) Disadvantage: Poor breed complementarity 39 kg lamb weaned per ewe exposed Suffolk rams x D(HSD) ewes Hampshire rams x S(DHS) ewes Male lambs and cull ewe lambs (system continues to rotate sire breed)
3-Breed Roto-Terminal Crossbreeding System S rams x DS ewes D rams x SD ewes S rams x D ewes Market Lambs Advantages: 1) All ewes (after start) and all lambs are crossbred – good use of individual and maternal hybrid vigor (67% of Mat HV, 67% & 100% Ind HV) 2) Good breed complementarity Disadvantage: ? 43 kg lamb weaned per ewe exposed D rams x SD ewes Hamp-sired lambs, S- and D-sired male lambs, some S- and D-sired ewe lambs Rotation (25-35 ewes) Terminal (65-75 ewes) SD ewes x Hamp rams DS ewes x Hamp rams SD ewes x Hamp rams (system continues)
Purebred vs Crossbred • For Jamaica it is better to utilize a crossbreeding programme rather than a purebreeding programme for small ruminant production.
Crossbreeding – Why? Paternal male x Maternal female Maternal male x Paternal female 1. Breed complementarity – Utilize the strong points of two or more breeds in a crossbreeding system to maximize performance. Good example: Imported Droper ram x St Elizabeth ewe Poor example: St. Elizabeth ram x imported Dorper ewe 2. Hybrid vigor or heterosis – increased performance of crossbreds compared to the purebreds that make up the cross.
Hybrid Vigor Example – 60-day Weaning Weight Dorper x Dorper lambs = 32kg St. Elizabeth x St. Elizabeth lambs = 20 lb. St. Elizabeth x Dorper and Dorper x St. Elizabeth lambs = 29 kg Average of purebred Dorper and St. Elizabeth lambs = (32 + 20) / 2 = 26 kg Hybrid vigor = 29 – 26= 3 kg % HV = ((crossbred – purebred) / purebred) x 100 = ((29 – 32) / 32) x 100 = (3 / 32) x 100 = .09 x 100 = 9 %
Final Comments on Crossbreeding • Good crossbreds result from good purebreds. • Don’t expect hybrid vigor to compensate for poor or inappropriate genetics. • Limit the number of breeds to those that have high levels of performance. • Hybrid vigor is maximized when no breeds are in common in the sire and dam. • More hybrid vigor is obtained when less related breeds are crossed. • An organized crossbreeding system is needed to take best advantage of hybrid vigor and breed complementarity